This invention relates to an open-end friction spinning machine having a plurality of spinning units, each containing two rollers that are arranged next to one another, form a wedge-shaped gap for the formation of yarn and are driven in the same rotational direction. Each spinning unit also contains a feeding device for fiber material to be spun that can be switched off via a yarn guard in the case of a yarn breakage, as well as an opening device, a suction device aimed into the wedge-shaped gap for the holding of the fiber material and of the yarn in the wedge-shaped gap, a withdrawal device withdrawing the spun yarn from the wedge-shaped gap, and a wind-up device winding the withdrawn yarn onto a wind-up spool that can be lifted off the driving roller.
In the case of an open-end friction spinning machine having one single spinning unit (EP-OS No. 34 427), it is known to switch off the device for the feeding of the fiber material in the case of a yarn breakage, while all other elements, especially the rollers and the wind-up spool continue to be driven. In the case of a yarn breakage, it may frequently happen that fibers or yarn residue or similar substances are located in the area of the wedge-shaped gap which will then continue to be twisted together by the rollers without being withdrawn from the area of the wedge-shaped gap. The result will then be a very hard twisted yarn-type structure which may lead to the danger of damage occurring at the rollers and/or their bearings, for example, by means of a deformation of the shell surfaces of the rollers. In addition, there is the danger that the continuously driven wind-up spool will be impaired with respect to its quality because the same layers of yarn will rotate on the driving roller and be pressed into the other layers of yarn. It will then also be difficult to find the broken yarn end required for the piecing process.
One objective of the present invention is the provision of an open-end friction spinning machine of the initially mentioned type such that after a yarn breakage, danger of damage to the rollers and/or their bearings will not exist and the wind-up spool itself will not be damaged.
This objective is achieved by equipping each spinning unit with means for lifting the wind-up spool off its driving roller and with means for interrupting the drive of the rollers. These means are controlled by the yarn guard of the spinning unit.
Thus it is provided that, in addition to an interruption of the feeding device for the fiber material, the rollers are stopped and the wind-up spool is lifted off the driving roller. Fiber residues are no longer twisted together in the wedge-shaped gap and cannot cause damage there. By means of the lifting of the wind-up tool, the outer layers of yarn are not pressed into the other layers of yarn so that there will be no damage to the wind-up spool and so that the broken yarn end is relatively easy to find.
In an advantageous development of the invention, it is provided that each spinning unit is equipped with means for interrupting or reducing the suction effect of the suction device which are controlled by the yarn guard. Remaining fibers or similar objects that may still be located in the wedge-shaped gap, will no longer be drawn into the wedge-shaped gap by means of the suction device so that they can be removed relatively easily.
In a first embodiment, it is provided that the yarn guard of each spinning unit is connected directly to the means for lifting off the wind-up spool, the means for interrupting the drive of the rollers and/or the means for interrupting or reducing the suction effect of the suction device. As a result, these functions are all triggered simultaneously by the yarn guard. In the case of a further development of the invention, it is provided that each spinning unit contains a control device to which the yarn guard is connected and which itself is connected with the means for lifting off the wind-up spool, the means for interrupting the drive of the rollers and/or the means for interrupting or reducing the suction effect of the suction device. This makes it possible, via the control device triggered by the signal of the yarn guard, to operate the individual means at indicated, coordinated points in time.
In another development of the invention, it is provided that the means for lifting off the wind-up spool are connected to the means for interrupting the drive of the rollers and/or the means for interrupting or reducing the suction effect of the suction device via a preferably mechanical connection. In this embodiment, the control movements are derived from only one control element and transmitted to all other elements. In a further development of this embodiment, it is provided that the mechanical connection has a locking device holding the means for interrupting the drive of the roller and/or for interrupting or reducing the suction effect of the suction device in the operating position against the effect of a biasing means.
In a further development of the invention, it is provided that the wind-up spools are held in spoolholders each of which is equipped with an actuating drive contanining a coupling to be closed during the operation. This ensures that the spoolholders can move during the spinning without being hindered, during which they are gradually lifted up corresponding to the diameter of the spools which increases during the spinning. The actuating drive, via the coupling, is connected with this spoolholder in such a way that always the same lifting movement is sufficient in order to still sufficiently lift the wind-up spool off the driving roller.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.